Various compositions and materials have been proffered in the past as being beneficial for relieving pain in human subjects. The field of analgesia dates back over 2000 years ago, known by archaeological evidence of earlier peoples ingesting opiates. In the modern era, opiates and semi-synthetic opiates are in extensive use, as well as non-opiate pain-relieving medications including non-steroidal anti-inflammatory drugs (“NSAIDS”), salicylic acid derivatives (aspirin) and naturopathic pain remedies. However, with the exception of salves, skin creams, ointments or lotions which include a topical anesthetic such as benzocaine, lidocaine, and camphor, there are currently no effective topical formulations useful for relieving pain.
Peripheral neuropathy is a specifically-named disease condition that affects a significant portion of the patient population, producing chronic pain patterns usually in the extremities of the human body. The pain characteristics of peripheral neuropathy are unique from the diffuse pain patterns of headache, backache, arthritis, arthralgia and rheumatism.
Pain distribution in peripheral neuropathy is related to the distribution of the affected nerve trunk involved. The intensity of the pain is directly related to the degree of intensity of nerve fiber damage. Once a peripheral neuropathy pain pattern is established, the pain pattern becomes a chronic pain that is recurring in nature. Thus, the pain associated with peripheral neuropathy is very specific, and is well-known in the art to be differentiable over other types of pain. Peripheral neuropathy is diagnosed using a standard diagnostic procedure that is unique to peripheral neuropathy, called nerve conduction tests (“NCT”). Nerve conduction tests are physician-directed, in the field of clinical neurology.
Peripheral neuropathy is damage or disease affecting nerves, which may impair sensation, movement, or other aspects of health depending on the type of nerve affected. Common causes include systemic diseases such as diabetes or leprosy, vitamin deficiencies, medications (e.g. systemic chemotherapy given for cancer treatments), traumatic injury, i.e., post-surgical following cancer surgery, excessive alcohol consumption, compression neuropathy secondary to Herniated Nucleus Pulposus, immune system disease sequelae, post-radiation treatments. In some instances, peripheral neuropathy can be inherited from birth.
Peripheral neuropathy can be either acute or chronic, and often occurs with more than one type of nerve tissue affected at the same time in an individual subject patient. Peripheral neuropathy is classified according to the type of nerve involved, or by its underlying cause. For instances in which the cause is unknown, peripheral neuropathy is described as idiopathic neuropathy.
Despite advances in the understanding of the pathophysiology of the metabolic causes of peripheral neuropathy, successful drug treatment of symptoms of peripheral neuropathy has been limited. The only three approaches currently approved by the United States Food and Drug Administration at the time of this writing for treating peripheral neuropathy are systemic drug therapies, involving: 1) tri-cyclic anti-depressant compounds; 2) anti-epileptic/anti-convulsant drugs; and 3) a long-acting opioid analgesic.
Prior to the present invention, there has been no known effective topical medicament useful for symptomatic relief of pain resulting from peripheral neuropathy, nor has there been any treatment for peripheral neuropathy approved by the United States Food and Drug Administration which is topically applied to the skin.